Although applicable to the contacting of any conductor paths, the present invention as well as its underlying object are explained with reference to the contacting of a platinum conductor path applied on a silicon substrate and an aluminum bonding land conductor path.
FIGS. 4a-c are a schematic depiction of a usual contacting arrangement, FIG. 4a being a plan view, FIG. 4b a cross-sectional view with a positive etching flank for the insulating layer, and FIG. 4c a cross-sectional view with a negative etching flank for the insulating layer.
In FIGS. 4a-c, reference character 10 designates a silicon substrate, 40 a platinum conductor path, 50 a CVD oxide, 53 a positive etching flank, 55 a negative etching flank, 60 an aluminum bonding land conductor path, 61 a web region, 62 a land region, 65 pinched-off aluminum pieces, 67 a detachment edge, L a contact hole, and Rc a contact hole junction resistance.
The arrangement shown in FIGS. 4a-c serves to transition the elongated platinum conductor path 40, via a narrow web region 61 of aluminum bonding land conductor path 60, into a wider land region 62 of the aluminum bonding land conductor path 60.
Platinum conductor path 40, running on substrate 10, is first covered completely with the insulating layer made of CVD oxide 50. In the end region of platinum conductor path 40, contact hole L is then opened up in CVD oxide 50 using a usual photolithographic etching process. Contact hole L is spaced away from the edges of the end region of platinum conductor path 40. Deposition and masking of aluminum bonding land conductor path 60 is then performed in order to yield the arrangement shown in FIG. 4a.
In order to evaluate the quality of the contact created in this fashion, contact hole junction resistance Rc between contact hole L in CVD oxide 50 and the corresponding land region 62 of aluminum bonding land conductor path 60 is measured.
Measurement of this contact hole junction resistance Rc serves in particular to characterize the degree to which the contact hole flanks are overlaid with aluminum, as will be explained in further detail below with reference to FIGS. 4b and c.
When contact hole L is opened in wet-chemical fashion, the result is usually the desired positive etching flanks 53 for the CVD oxide, which ensure good overlay of the contact hole flank with aluminum, and thus a low contact hole junction resistance Rc (FIG. 4b).
This standard process can, however, result locally on a wafer in undesired negative etching flanks 55 for the CVD oxide, and thus in high contact hole junction resistances Rc (FIG. 4c). They may be caused by an inhomogeneously grown CVD oxide layer 50 and/or by contaminants at the interface between CVD oxide layer 50 and platinum conductor path 40. Such negative etching flanks at the contact hole edges result, in particular, in pinched-off pieces 65 and detached edges 67, which can result in the elevated contact hole junction resistance Rc and, in the worst case, in an break in aluminum bonding land conductor path 60 and thus failure of the component in question. It has proven disadvantageous that with the aforementioned known approach, a certain proportion (typically a few %) of the components exhibit an elevated contact hole junction resistance Rc with the standard process.